1. Field of Invention
The present invention relates to an LED lighting apparatus, and more particularly to an apparatus which concentrates the projection of an LED light source by a linear reflective surface.
2. Description of Related Arts
LED lightings are widely used these days for its numerous benefits such as energy saving, small size, long life, and durability. However, currently the overall light output of LED is still relatively low, extra apparatus are needed to concentrate the light output for increasing the intension.
LED is a solid state semiconductor device. It directly produces visible light when the semiconductor crystal is excited. It can be regarded as a small area light source and project light radially. Generally the semiconductor crystal is packed in a transparent package to shape its light beam patterns. The light beam patterns are typically within 90 to 120 degree angles. For a standard 90 degree LED, the relative luminous intensity is illustrated in FIG. 6. Referring to FIG. 6, the intensity is the highest at zero degree angle and drops to 50% at +/−45 degree. The light spread in a large angle of range. The relative luminous flux is about peaked within the 30 to 40 degree range.
Most of existing LED lightings is more or less following the output beam patterns. As mentioned above, this performance is not efficient, and wastes a lot of energy. If not sufficient brightness can be provided, LED with higher power is needed. Obviously this will cost more, and generate more heat. One solution is using single reflection curved surface to focus the LED light for the desired light patterns. For example, the reflection curved surface is parabolic. The LED light source is location on the focal point of the paraboloid and projecting light onto the reflection curved surface. The light rays are reflected once by the surface to form a parallel beam. This will concentrate the light in a limited area (spot). But the curved reflection surface still has a problem. Since the light ray with the zero degree will be reflected in the same path, and will be blocked by the LED itself, at the same time all other light rays are reflected in parallel, a black spot is formed in the center of the light beam. It needs to be avoid because most of the time the center of the light beam should have the highest brightness.